Shrouded rotor blade structure

ABSTRACT

A SHROULDED ROTOR BLADE STRUCTURE FOR AN ELASTIC FLUID AXIAL FLOW TURBINE OR COMPRESSOR COMPRISING AN ANNULAR SERIES OF SEGMENTS ARRANGED IN END-TO-END ABUTMENT WITH EACH OTHER. EACH SEGMENT HAS TWO TENONS OF SEMICYLINDRICAL SHAPE, WHICH HEREINAFTER WILL BE CALLED SEMITENONS, ONE ON EACH END, EXTENDING RADIALLY OUTWARD WHEREIN THE FLAT FACES OF THE SEMITENONS ABUT THEIR MATING HALVES ON THE ADJACENT SEGMENTS FORMING TWO-PIECE TENONS. RINGS TIGHTLY ENCIRCLE THE TENON STRUCTURES TO MAINTAIN THE SEMITENONS IN ABUTMENT. THE TENONS ARE DEFORMED LOCKING THE RINGS IN PLACE.

United States Patent Inventor Ralph E. McGinnis Folsom, Pa.

Appl. No. 857,946

Filed Sept. 15, 1969 Patented June 28, 1971 Assignee WestinghouseElectric Corporation Pittsburgh, Pa.

SHROUDED ROTOR BLADE STRUCTURE l0 Claims,3Drawlng Fig.

U.S.Cl. 416/191, 416/195 lnt.Cl 1-0ld 5/22 FieldofSearch 416/191,189,195,196

[56] References Cited UNITED STATES PATENTS 2,366,142 12/1944 Allen416/191 3,070,350 12/1962 Stewart 416/191 Primary Examiner- Everette A.Powell, Jr. Attomeys-A. T. Stratton, F. P. Lyle and F. Cristiano, Jr.

ABSTRACT: A shrouded rotor blade structure for an elastic fluid axialflow turbine or compressor comprising an annular series of segmentsarranged in end-to-end abutment with each other. Each segment has twotenons of semicylindrical shape, which hereinafter will be calledsemitenons, one on each end, extending radially outward wherein the flatfaces of the semitenons abut their mating halves on the adjacentsegments forming two-piece tenons. Rings tightly encircle the tenonstructures to maintain the semitenons in abutment. The tenons aredeformed locking the rings in place.

PATENTEDJUNQB 1911 3588.279

NESSES INVENTOR RALPH E. McGlNNIS SIIIROUDED ROTOR BLADE STRUCTUREBACKGROUND TO THE INVENTION i are A. .l. Partington, US. Pat. No.3,367,629 and P. D. Saunders, U.S. Pat. No. 3,367,630 both issued onFeb. 6, 1968 and both assigned to the same assignee as this invention.

This invention provides a novel structure employing a continuous shroudwhich minimizes vibrational stresses and minimizes thermal-fatiguestrains in the blade structure.

SUMMARY OF THE INVENTION In accordance with this invention a turbine orcompressor is provided with an annular row of rotor blades and a shroudstructure surrounding the blades. The shroud consists of an annularseries of segments which are on the outermost portion of the blades tipsand integral therewith, arranged in end-toend abutment with each other.On the opposite ends of each segment is a semitenon extending radiallyoutward with respect to the axis of rotation of the rotor. Eachsemitenon has a flat face flush with the edge portion of the segmentfacing the flat face of the semitenon on the adjacent segment. Thesemitenons are substantially identical to each other in size and shape.A two-piece tenon is formed when the flat face of a semitenon abuts itsmating half on the adjacent segment. A cincture encompasses thesemitenons to insure the abutting relation. The tenon is deformed,holding the cincture in compressive abutment between the tenon and theshroud segment.

Elastic fluid flows axially through the turbine at high temperature andpressure, driving the rotor structure. As the shroud expands orcontracts due to the centrifugal and thermal forces, the stressesconcentrate in the extruding portions of the shroud which are the tenonstructures. The semitenons are flexible and deflect, relieving part ofthe forces transferred to the cincture and minimizing the centrifugaland thermal induced strains in the blade structure.

DESCRIPTION OF THE DRAWINGS Reference may be had to the followingdrawings for a better understanding of the nature and objects of theinvention in which:

FIG. 1 is a view in perspective of a portion of a bladed rotor structurein accordance with the invention shown in the various stages offabrication;

FIG. 2 is a developed view in plan of the shroud portion shown in FIG.1; and

FIG. 3 is an enlarged sectional view of the tenon structure taken alongline III-III in FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows a fragmentary viewof a rotor structure 9, only part of which has been shown, it beingunderstood that the structure is part of an elastic fluid axial flowturbine or compressor (not shown). The FIG. shows the construction ofthe invention from the initial to the final stages where in sequentialorder from the top of the FIG. there is a semitenon 18, a two-piecetenon 22 before riveting, an exploded view of a tenon structure 24, atenon structure 24a after riveting, and a sectional view of a rivetedtenon structure 240.

The rotor structure includes a portion of a rotor 10, a'transverseannular row of blades 11, which are substantially identical to eachother, and a shroud structure 12 surrounding the outennost tips of theblades 11. The blades 11 are of the usual air foil contour, as wellknown in the art, and are attached to the rotor 10 by means of rootportions 13 disposed in a suitable groove 14 in the rotor The blades 11extend radially outward relative to the longitudinal axis of rotation ofthe rotor (not shown) and they may constitute one row of a multistageaxial flow turbine.

The shroud 12 comprises an annular series of segments or blade covers15, which are integral with the outermost tips of the blades 11. Thesegments 15 are substantially identical to each other, and, as bestindicated in FIG. 2, for purposes of illustration, are of parallelogramshape in plan. The segments are in end-to-end relationship forming acontinuous 360 shroud.

Each blade 11 has two semitenons 17, 18 integral therewith which mayalso be integral with the segment 15. The semitenons 17, 18 are formedin mating halves. There is one semitenon 17 on the left end of segment15 and one semitenon 18 on the right end. The left semitenon 17 has aflat face 20 and the right semitenon 18 has a flat face 21 which arelongitudinal of the blade 11. The flat faces 20, 21 of the semitenons17, 18 are flush with the edge portions of the segment 15 and areoriented towards the flat faces 21, 21 of the adjacent semitenons 18,17. The faces 21, 21 of the semitenons 17, 18 abut the faces 21, 20 oftheir mating halves 18, 17 on the adjacent segments forming a two-piecetenon 22. From a view looking into either edge of the segment 15, thesemitenons 17, 18 and the edge portions of the segment 15 form aninverted T. This is best illustrated in FIG. 1 from a view looking intothe leftwardmost face 20 of the semitenon 17 on segment 15. Thesemitenons 17, 18 are arranged in an annular row along the center of thesegments 15 and the row is curved conforming to the curvature of theshroud 12. The two-piece tenon 22 may be an irregular, nonsymmetricalsolid, or a regular solid in which all angles and sides are equal, suchas a polygon, or the tenon may be a solid of revolution which hascircular cross section taken parallel to the axis of rotation of therotor, such as a cylinder as shown in FIGS. 1 and 2.

Fastening means 23 may be a cincture which conforms to the shape of thetenon 22 and interacts therewith to firmly hold the abutting semitenons17, 18 together and to thereby secure the adjacent segments 15 inabutting end-to-end relationship. For purposes of illustration, and asbest shown in the exploded view of FIG. 1, the cinctures are cylindricalrings 23. Each ring 23 fits over the cylindrical tenon 22 to securelyencircle it to maintain the semitenons 17, 18 and the segments 15 inabutting relationship.

As best illustrated in the sectional view in FIG. 1 and in FIG.

3, the tenon 22 is deformed as indicated by 220 by riveting andmushrooms over the fastening means or cincture 23 to maintain thecincture in compressive abutment between the tenon 220 the segment 15.The riveting locks the cincture 23 in place to prevent loss of thecincture in operation.

The resulting structure is a continuous 360 shroud which eliminates theresonant condition and thereby the resulting stresses and minimizes theeffect of the partial admission loading stresses. Furthermore, as thestructure goes through a thermal cycle, thermal strains and stresseswill result due to the temperature differential between the rotor 10 andthe shroud 12. The semitenons 17, 18 will flex minimizing the thermalstrains and stresses and because the cincture 23 is in abutment with thesemitenons, it absorbs some of the thermal forces, further minimizingthe thermal strains.

Although the tenon 22 has been shown for purposes of illustration to bea two-piece tenon, and has been defined as semitenon, the tenon need notbe limited to two-pieces. Accordingly, in some of the claims, the termpartial-tenon has been employed.

Since numerous changes may be made in the abovedescribed construction,and different embodiments of the invention may be made without departingfrom the spirit and scope thereof, it is intended that all the mattercontained in the foregoing description or shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

lcIairn:

1. ln elastic fluid utilizing apparatus,

a rotor having a transverse annular row of blades,

a continuous shroud surrounding the radially outermost tips of theblades,

said shroud comprising an annular series of segments arranged inend-to-end abutment with each other, partial-tenons extending radiallyoutward on opposite ends of said segments,

said partialtenons abutting the partial-tenons on the adjacent segmentsforming multipiece tenons,

and fastening means connecting said multipiece tenons to firmly securethe segments in abutting relationship.

2. The structure defined in claim 1 wherein the shroud segments areintegral with the blades and substantially identical to each other.

3. The structure defined in claim 1 wherein the partialtenons aresubstantially identical mating halves.

4. The structure defined in claim 1 wherein the partialtenons areintegral with the blades.

5 The structure defined in claim 1 wherein the partialtenons have flatfaces'and the edge portions of the segments and the flat faces form Ts.

6. The structure defined in claim 3 wherein the partialtenons abut theirmating halves on the adjacent segments to form two-piece tenons.

7. The structure defined in claim 3 wherein the partialtenons are ofsemicylindrical shape.

8. The structure defined in claim 1 wherein the fastening means arecinctures which encompass the tenons.

9. The structure defined in claim 8 wherein the tenons are deformed byriveting to thereby hold the cinctures in compressive abutment.

10. The structure defined in claim 1 wherein the partialtenons aresubstantially identical mating halves,

said partial-tenons abutting their mating halves on the adjacentsegments to form two-piece tenons,

said partial-tenons being semicylindrical in shape, and

the fastening means being rings encircling the two-piece tenons.

